Method of forming a bladder assembly

ABSTRACT

This invention relates to the art of pressure vessels, more particularly of the type using a deformable bladder having a cylindrical mouth of relatively large diameter compared to the diameter of the bladder and which snugly encompasses an annular metal retaining member, being secured thereto by curing a layer of rubber interposed between said annular retaining member and the adjacent portion of said bladder mouth.

waited States Meant 1111 3,627,612

[72] Inventor Edward M. Greer [56] References Cited Beverly Hills Calif-UNITED STATES PATENTS 211 Appl. N0. 829,017

[22] Filed y 29, 1969 1,359,594 11/1920 Harrls 156/309 2,062,248 11/1936156/308 [45] Patented Dec. 14, 1971 2,304,718 12/1942 Swan 156/309 [73]Ass1gnee Greer Hydraulics, lnc.

2,337,555 12/1943 Hoskmg 156/308 Angelescal'f' 3 387 839 6/1968 Milleret al 156/310 Original application Nov. 17, 1966, Ser. No. 595,164, nowPatent No. 3,494,378, Primary Examiner Reuben Ep ein dated Feb. 10,1970. Divided and this AlwrneyArthur l in application May 29, 1969, Ser.No. 829,017

ABSTRACT: This invention relates to the art of pressure vessels, moreparticularly of the type using a deformable bladder [54] METHOD OFFORMING ABLADDER ASSEMBLY having a cylindrical mouth of relatively largediameter com- 9 Claims, 5 Drawing Figs. pared to the diameter of thebladder and which snugly encompasses an annular metal retaining member,being secured U.S.Cl (2356/5333 thereto by curing a layer of rubberinterposed between Said j annular retaining member and the adjacentportion of said [50] FleldofSeareli 156/308 bladder mouth 309 20 2? n 23r .28 J2 I -26 PATENIEDHEEMBYI 316327.612

SHEET 1 BF 2 FIG] INVENTOR EDWARD M. CREEK ATTORNEY METHOD OF FORMING ABLADDER ASSEMBLY This application is a Division of copending applicationSer. No. 595,164, filed Nov. 17, 1966, now Pat. No. 3,494,378, datedFeb. 10, 1970.

As conducive to an understanding of the invention, it is noted thatwhere a pressure vessel of the above type has a rigid cylindrical shellor container in which a metal retaining member is positioned, that issecured in fixed position adjacent one end of the container, and adefonnable partition such as a bladder of resilient stretchablematerial, illustratively of synthetic rubber, is positioned in saidcontainer with the periphery or mouth of the bladder secured to theretaining member, unless a dependable seal is formed between theperiphery or mouth of the bladder and the retaining member and theperiphery or mouth of the bladder and the container, leakage will occurwith resultant failure of the unit.

Where the periphery or mouth of the bladder is mechanically clampedbetween the retaining member and the container, if there should be anyirregularities or lack of concentricity in the retaining member, slightopenings or passageways will occur with resultant gas leakage.

Where the bladder which has already been cured is cemented to the metalretaining member, an unreliable bond will occur which under the constantstress resulting from the pressure in the unit and the constant stretchand relief from stretch during use of the unit, may break the cementedbond with resultant leakage.

Furthermore since the bladder stretches considerably in use and itsoverall stretch may be as high as 40 percent, which reacts against theportion of the bladder secured to the retaining member, unless adependable bond is effected the bladder may pull away from the retainingmember with resultant failure of the unit.

It is accordingly among the objects of the invention to provide apressure vessel of the above type, and method for forming the same,which may readily be fabricated at relatively low cost from relativelyinexpensive parts in a relatively simple manner, without need forholding close tolerances, with assurance that the periphery or mouth ofthe preformed bladder will remain securely and permanently bonded to themetal retaining member positioned in the container.

According to the invention these objects are accomplished by thearrangement and combination of elements hereinafter described and moreparticularly recited in the claims.

In the accompanying drawings in which are shown various possibleembodiments of the several features of the invention.

FIG. 1 is a longitudinal sectional view of a pressure vessel accordingto one embodiment of the invention,

FIG. 2 is a detail sectional view on an enlarged scale showing the mouthof the bladder bonded to the retaining member.

FIG. 3 is a detail sectional view of a jig for holding the retainingmember when the bladder is being bonded thereto,

FIG. 4 is a view similar to FIG. 1 of another embodiment of theinvention, and

FIG. 5 is a fragmentary sectional view of the bladder of FIG. 4.

Referring now to the drawings, as shown in FIG. 1, the pressure vessel,which in the illustrative embodiment is a pressure accumulator,comprises a shell or container of rigid material such as aluminum,steel, brass or the like, capable of withstanding the pressures to whichthe unit will be subjected in use.

The container 10 is substantially cylindrical as shown, having a mouth11 and a rounded lower end 12 having an axial opening 13 therein whichis conformed to define an inwardly extending annular flange 14 on whichis seated the flange 15 of a sleeve or fitting 16 which is secured inplace as by welding at 17 and defines the liquid port 18 of the pressurevessel.

As is clearly shown in FIG. I, the inner end of the sleeve 16 has aperforated plate 18 extending transversely thereacross and the sleeve isdesirable externally threaded as at 19 to permit connection thereto of acorrespondingly threaded fitting (not shown).

Positioned in the mouth of the container 10 is metal retaining member 21which also forms the cover for the mouth of the container. The member 21illustratively has a curved central portion 22 with an axial opening 23in which a fitting 24 is secured to retain an air valve, for example,(not shown). The periphery 25 of the central portion 22 is reverselybent to define a mounting sleeve 26, the outer edge of which isoutwardly bent to define an annular shoulder 27. Rising from theperiphery of shoulder 27 is a retaining sleeve 28 of outer diametersubstantially equal to the inner diameter of the container 10.

Secured to the outer surface of mounting sleeve 26 is a deformablepartition 31 illustratively a bladder of synthetic rubber such as Buna,Butyl, Neoprene or similar material having like characteristics.

As is clearly shown in FIG. 2, the mouth of the bladder 31 has anelongated thickened rim 32 which is of length substantially equal tothat of the mounting sleeve and the lower edge of the outer portion 32aof rim 32 is beveled as at 34 to form a sealing lip or chevron seal 34a.

To assemble the pressure vessel, a layer 35 of uncured rubber,preferably but not necessarily of the same type as that from which thebladder 31 is formed, is positioned around the mounting sleeve 26 whichpreviously has been cleaned and roughened as by a wire brush, forexample. The layer 35 may be sprayed or painted on, or a strip ofsuitable material may be provided and in the illustrative embodimentshown, such a strip is provided. Thereupon, the mouth of the bladderwhich normally is approximately of diameter five (Spercent) percent lessthan the outer diameter of sleeve 26 is stretched so that it will bepositioned tightly around the sleeve 26 and the uncured strip 35 ofrubber, the inner surface 321: of rim 32 of the bladder 31 also havingbeen cleaned and roughened prior to mounting.

Thereupon, the cover member 21 with the bladder mounted thereon as abovedescribed is subjected to heat to cure the strip 35. To this end theassembly preferably is positioned in a jig 61 which has a cylindricalopening 62 with a beveled mouth 63. When the cover member is forced intoopening 63, the rim 32 will be compressed as shown, between thecylindrical opening 62 and the sleeve 26.

With the cover member 21 thus positioned in jig 61, the heating elements64 in the jig 61 are energized so that the strip 35 will be cured tobond the rim 32 of the bladder 31 to the sleeve 26. Different materialsrequire different temperatures and time cycles. However, using Buna N,for example, as the composition from which the bladder is formed, withthe strip 35 also of Buna N, a temperature of from approximately 250 to350 F. for approximately 10 to 40 minutes is sufficient to completelycure the strip 35 and effect a permanent bond between rim 32 and sleeve26, the strip 35 becoming an integral part of rim 32.

By reason of the sue of the uncured layer of rubber 35, a highlyeffective bond will be effected to the metal sleeve 26 which could notbe made if the cured rubber bladder was cemented or otherwise adhesivelysecured to the metal sleeve 25. Furthermore, by reason of the checkingeffect produced by the stretched rim of the bladder, the uncured rubberstrip 35 will be forced into intimate engagement with both the innerportion 32b of the rim 32 of the bladder 31 and the outer surface ofsleeve 26 so that no air holes or passageways will be present betweenthe rim 32 and sleeve 26 even if there are slight irregularities in themetal sleeve 26.

After the rim 32 of the bladder 31 has been bonded to the sleeve 26, asabove described, the cover member 21 with the bladder bonded thereto, isthen forced into the open mouth of the container 10. As shown in FIG. 2,in its bonded condition, the outer portion 32a of rim 32 extendsslightly beyond the plane of the outer surface of retaining sleeve 28and the upper edge 38 of the rim 32 is slightly spaced from annularshoulder 27 as at 39.

Thus, when the assembled cover member 21 is forced into the mouth of thecontainer, the rim 32 will be compressed between the wall of thecontainer and the sleeve 26 as shown in FIG. 1. As a result of the space39, the upper edge 38 of rim 32 will be free to move upwardly until itabuts against shoulder 27 and the lower edge of rim 32 will movedownwardly and the cheveron lip or seal will be compressed between thewall of the container and the lower edge 25 of sleeve 26 to define aneffective seal.

Thereupon, the free edge 41 of the container is reversely bent as at 42over the upper edge 43 of sleeve 28 securely to retain the cover member21 in fixed position.

In use of the pressure vessel, the chamber 46 defined by the bladder ischarged with gas under pressure through fitting 24 which is then closed.Thereupon, fluid such as hydraulic liquid under pressure is forcedthrough port 18 to charge the chamber 47 on the other side of thebladder and compress the gas in the latter.

Since the inner portion 32b of the rim 32 is dependably bonded to sleeve26, there will be no possibility of gas under pressure leaking fromchamber 46. As the outer portion 32a of rim 32 is pressed tightlyagainst the wall of the container an effective seal is provided which isenhanced by the chevron lip seal 340 at the lower edge of rim 32. Thus,as the hydraulic liquid under pressure in chamber 47 reacts against thechevron lip 34a, as at 51, it will force the lip outwardly against thewall of the container for efi'ective sealing action.

In the embodiment shown in F I63. 4 and 5, parts corresponding to thosein FIGS. 1 to 3 have the same reference numerals primed.

In this embodiment, as shown in FIG. 4, the shell or container has theend 11' thereof remote from the rounded lower end 12', substantiallyclosed, being provided with a relatively small port 70.

More particularly the end 12' is defined by a cap 12a which is securedas by welding at 71 to the open end 72 of the cylindrical portion 10a ofthe container 10'.

The retaining member 21' of FIG. 4 illustratively is substantiallycup-shaped having a floor 22' with an axial opening 23 and a dependingannular wall 74 with an external annular recess 75.

A gas fitting 76 having an annular flange 77 at its inner end, extendsthrough opening 23 in the floor 22 and is secured thereto as by welding.The stem of fitting 76 extends through the opening 70 in the end ofcontainer 10' and by means of a nut 78 screwed on the threaded end ofthe stem 76, the floor 22' of retaining member 21' is moved against theundersurface of end 11 of the container. Desirably, a sealing washer 79encompasses the stem 76 between the floor 22 and the end 1 l of thecontainer.

The rim 32' of the bladder 31' is bonded to the annular wall of recess'75 in the same manner as described with respect to the embodiment ofFIG. 1. Thus, the rim 32' of bladder 31' is stretched to encompass theannular wall 74 which previously has been provided with a layer 35' ofuncured rubber as illustratively shown in FIG. 4, which is then heatedto efiect curing thereof for effective bonding action. It is understoodthat after curing, the layer 35 will become an integral part of rim 32'.

The pressure vessel shown in FIG. 4 is assembled by inserting theassembly comprising the retaining member with the bladder bonded theretothrough the open end 72 of container 10', so that the stem 76 protrudesthrough port 70. Thereupon, the nut 78 is tightened, drawing the flangeof the retaining member 21' against the end 11' of the shell therebycompressing the gasket 79.

The cap 12a is positioned over the end 72 of the shell and welded inposition.

In the embodiment shown in FIGS. 4 and 5, since the inner portion of rim32' is also dependably bonded to the annular wall 74, there will be nopossibility of gas under pressure leaking from chamber 46. As the outerportion 32'a of rim 32' is pressed against the wall of the container, aneffective seal will be provided between the container wall and theretaining member 21 to prevent leakage of oil.

As many changes could be made in the above method and article, and manyapparently widely different embodiments of this invention could be madewithout departing from the scope of the claims, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

l. The method of forming a bladder assembly which comprises the steps ofpositioning a layer of uncured rubber on the surface of an annular metalmounting sleeve, thereupon positioning the rim of a cured bladder,having an inner diameter at its mouth at least 5 percent less than theouter diameter of the mounting sleeve, so as to encompass the mountingsleeve and the layer of uncured rubber thereon snugly engage suchuncured layer, and then heating such uncured layer at a temperature andfor a sufficient time fully to cure such layer, whereby the rim of thecured bladder will be dependably bonded to said metal sleeve.

2. The method set forth in claim 1 in which the uncured layer of rubberis the same composition as the bladder.

3. The method set forth in claim 1 in which the layer of uncured rubberis a strip that is wound around the metal sleeve.

4. The method set forth in claim 1 in which the uncured layer of rubberis sprayed onto the metal sleeve.

5. The method set forth in claim 1 in which the uncured layer of rubberis brushed onto the metal sleeve.

6. The method set forth in claim 1 in which the mounting sleeve with theencompassing bladder is positioned in a jig which securely retains therim of the bladder against the sleeve during the heating step.

7. The method set forth in claim I in which the uncured layer is heatedat a temperature of approximately 250 to 350 F. for approximately 10 to40 minutes.

8. The method set forth in claim 1 in which the bladder is formed fromBuna N and the uncured layer is heated at a temperature of approximately300 F. for thirty minutes.

9. The method set forth in claim 1 in which the diameter of the mouth ofthe bladder is at least five (5 percent) percent less than the outerdiameter of the mounting sleeve so that when the mouth of the bladderencompasses the mounting sleeve, the rim of the bladder will snuglyengage the uncured layer of rubber.

2. The method set forth in claim 1 in which the uncured layer of rubberis the same composition as the bladder.
 3. The method set forth in claim1 in which the layer of uncured rubber is a strip that is wound aroundthe metal sleeve.
 4. The method set forth in claim 1 in which theuncured layer of rubber is sprayed onto the metal sleeve.
 5. The methodset forth in claim 1 in which the uncured layer of rubber is brushedonto the metal sleeve.
 6. The method set forth in claim 1 in which themounting sleeve with the encompassing bladder is positioned in a jigwhich securely retains the rim of the bladder against the sleeve duringthe heating step.
 7. The method set forth in claim 1 in which theuncured layer is heated at a temperature of approximately 250* to 350*F. for approximately 10 to 40 minutes.
 8. The method set forth in claim1 in which the bladder is formed from Buna N and the uncured layer isheated at a temperature of approximately 300* F. for thirty minutes. 9.The method set forth in claim 1 in which the diameter of the mouth ofthe bladder is at least five (5 percent) percent less than the outerdiameter of the mounting sleeve so that when the mouth of the bladderencompasses the mounting sleeve, the rim of the bladder will snuglyengage the uncured layer of rubber.